1. Field of the Invention
The invention is based on a valve cartridge for a solenoid valve.
2. Description of the Prior Art
A valve cartridge for a conventional solenoid valve, in particular for a hydraulic unit which is used for instance in an anti-lock brake system (ABS) or a traction control system (TCS) or an electronic stability program system (ESP system), is shown in FIGS. 1 and 2; FIG. 1 is a schematic longitudinal section and a FIG. 2 is a schematic cross section through the valve cartridge. As can be seen from FIG. 1, the valve cartridge 1 for the conventional solenoid valve has a capsule 4, a valve insert 2, a tappet 3, a restoring spring 8, and an armature 6. In the production of the solenoid valve, the capsule 4 and the valve insert 2 of the valve cartridge 1 are joined together by press-fitting, and the valve cartridge 1 is hydraulically sealed off from the atmosphere by a sealing weld. In addition, the valve insert 2 absorbs the pressure forces that occur in the hydraulic system and conducts them onward via a calked flange to a calked region, not shown, of a fluid block. The valve insert 2 also conducts a magnetic flux, initiated by a magnet unit not shown, onward axially via an air gap in the direction of the armature 6. The valve insert 2 furthermore receives the so-called valve body 7, which includes a main valve seat 7.1 into which a closing element 3.2 of the tappet 3 plunges sealingly, in order to realize the sealing function of the solenoid valve. As can also be seen from FIG. 1, the tappet 3 and the restoring spring 8 are guided in an inner bore 2.1 of the valve insert 2.
As seen from FIG. 2, the inner bore 2.1 of the valve insert 2 as a rule has a completely or very nearly approximated circular shape, in which the tappet 3 is guided. To compensate for the volume that the tappet 3 positively displaces upon its axial motion caused by the magnetic flux initiated by the magnetic unit, and for ventilation and filling, at least one axially extending volumetric-compensation groove 5 is machined into the tappet 3, which complicates the shape of the tappet casing 3.1, as can also be seen from FIG. 3. This complicated shape of the tappet casing 3.1 puts limits on the possible production methods that can be used for the tappet 3. FIGS. 4a and 4b show an alternative embodiment according to the present invention of the valve insert 2′, which is produced by curling a sheet-metal strip 2″, so that the inner passage 2.1′ for guiding the tappet 3 is created only after the curling and is formed by a corresponding surface 2.1″ of the sheet-metal strip 2″.